Monoclonal antibody and gene encoding the same, hybridoma, pharmaceutical composition, and diagnostic reagent

ABSTRACT

A novel human monoclonal antibody specifically recognizing cancer cells such as non-small cell lung cancer, pancreatic cancer and gastric cancer cells is produced by hybridomas which are obtained by fusing lymphocytes derived from a cancer tissue of a cancer patient with mouse myeloma cells. An anti-cancer drug is obtained by using the antibody alone or anchoring the antibody on the surface of a liposome containing a toxin or an anti-cancer drug encapsulated therein. More specifically, an anti-cancer drug is obtained by using an antibody, in which variable region of its heavy chain comprises the amino acid sequence of SEQ ID NO: 115 and variable region of the light chain comprises the amino acid sequence of SEQ ID NO: 117, alone or anchoring the antibody on the surface of a liposome containing a toxin or an anti-cancer drug encapsulated therein.

TECHNICAL FIELD

The present invention relates to a novel monoclonal antibody useful for diagnosis and therapy of cancer, and a DNA encoding such a monoclonal antibody, a hybridoma producing such an antibody, and a pharmaceutical composition and a diagnostic reagent, each of which contains such an antibody.

BACKGROUND ART

In the field of cancer therapy, targeting therapy against a specific type of cancer cell has been studied so far for the treatment of solid cancer on which no therapeutic agent shows sufficient effect. In such targeting therapy, a monoclonal antibody that specifically recognizes cancer cells is effective. However, the use of a mouse monoclonal antibody has some problems such as difficulty of repetitive administration because of side effects such as anaphylaxis caused by an immune response (Proc. Natl. Acad. Sci. U.S.A. vol.86, p 4220, 1989).

For solving such problems, attempts have been conducted to obtain monoclonal antibodies with reduced side effects. A technology for producing a chimeric antibody in which constant region is replaced with that of human antibody by genetic engineering, a technology for producing a humanized antibody in which all regions except for hypervariable regions are replaced with those of human antibody, etc. are known. However, a complete human monoclonal antibody has been desired from the viewpoint of reducing side effects. As a method of obtaining a complete human monoclonal antibody, there is a hybridoma method using a lymphocyte derived from human (Cancer Res. vol.45, p 263, 1985). Although there is a few report about a human monoclonal antibody that reacts cancer cells (JP3236667 etc.), preparation of human monoclonal antibodies which adequately react with cancer cells has been still very difficult because of the reasons that it is very difficult to conduct passive immunity for the purpose of obtaining human B cells which produce a desired antibody, and that any efficient methodology which allows infinite reproduction of antibody-producing cells has not been established yet.

Even under such circumstances, some monoclonal antibodies which exhibit a killing-effect or anti-proliferative effect on specific cancer cells by itself or in combination with anti-cancer drugs have been developed using a humanized antibody technology or the like. In recent years, application of an anti-Her2-humanized antibody HERCEPTIN™) to breast cancer (Oncology vol. 63 Suppl 1, pp 25-32, 2002), clinical trials using an anti-EGF receptor antibody (Semin Oncol. vol. 29, No. 5 Suppl 14, pp 18-30, 2002), or an anti-VEGF (vascular endothelial growth factor) antibody (Semin Oncol. vol. 29, No. 6 Suppl 16, pp 10-14, 2002), and the like have been reported. However, any antibody, which can be used for targeting therapy for cancers including a non-small cell lung cancer from which many patients are suffering or refractory cancers such as pancreatic cancer, has not yet been developed. For treating such types of cancer, the acquisition of a monoclonal antibody having high specificity to cancer tissue with reduced side effects has been desired.

Vimentin is a cytoskeletal filament protein of a mesenchymal or nonepithelial cell, and it is known that its gene expression increases upon cell stimulation (Mol Cell Biol. 1987, vol. 7, No. 11, p3908-15). In addition, it is known that the expression of vimentin is not found in normal epithelial cells, whereas high expression of vimentin is found in cytoplasm of some poorly-differentiated tumor cells such as those of pulmonary adenocarcinoma, gastric cancer, endometrial carcinoma, or embryonal cell carcinoma (Mol Cell Biol. 1987, vol. 7, No. 11, p 3908-15). However, a phenomenon that vimentin functions as an antigenic protein has not been known.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a monoclonal antibody useful for diagnosis and treatment of cancer, particularly of non-small cell lung cancer, pancreatic cancer, and gastric cancer with reduced side effects.

The inventors of the present invention have made extensive studies to provide a monoclonal antibody that can be used in targeting therapy on cancer tissues. As a result, they prepared hybridoma cells that produce a novel human monoclonal antibody capable of specifically recognizing cancer cells such as HLC-1, PANC-1 or MKN45, and found that anti-cancer drug useful in targeting therapy can be obtained by using such an antibody. Accordingly, they completed the present invention.

That is, the present invention provides the followings.

(1) A monoclonal antibody, wherein variable region of heavy chain of said monoclonal antibody comprises amino acid sequences of SEQ ID NOS: 86, 88 and 90.

(2) The monoclonal antibody according to (1), wherein the variable region of the heavy chain comprises an amino acid sequence of SEQ ID NO: 82.

(3) The monoclonal antibody according to (1), wherein the variable region of the heavy chain comprises an amino acid sequence of SEQ ID NO: 115.

(4) A monoclonal antibody, wherein variable region of the light chain of said monoclonal antibody comprises amino acid sequences of SEQ ID NOS: 92, 94 and 96.

(5) The monoclonal antibody according to (4), wherein the variable region of the light chain comprises an amino acid sequence of SEQ ID NO: 84.

(6) The monoclonal antibody according to (4), wherein the variable region of the light chain comprises an amino acid sequence of SEQ ID NO: 117.

(7) A monoclonal antibody, wherein variable region of the heavy chain of said monoclonal antibody comprises amino acid sequences of SEQ ID NOS: 86, 88 and 90, and variable region of the light chain of said monoclonal antibody comprises amino acid sequences of SEQ ID NOS: 92, 94 and 96.

(8) The monoclonal antibody according to (7), wherein the variable region of the heavy chain contains an amino acid sequence of SEQ ID NO: 82, and the variable region of the light chain comprises an amino acid sequence of SEQ ID NO: 84.

(9) The monoclonal antibody according to (7), wherein the variable region of the heavy chain comprises an amino acid sequence of SEQ ID NO: 115, and the variable region of the light chain comprises an amino acid sequence of SEQ ID NO: 117.

(10) The monoclonal antibody according to any one of (1) to (9), wherein said monoclonal antibody is a human antibody.

(11) A DNA which encodes the monoclonal antibody according to any one of (1) to (10).

(12) The DNA according to (11), wherein a region that encodes variable region of the heavy chain comprises nucleotide sequences of SEQ ID NOS: 85, 87 and 89, and a region that encodes variable region of the light chain comprises nucleotide sequences of SEQ ID NOS: 91, 93 and 95.

(13) The DNA according to (11) or (12), wherein the region that encodes the variable region of the heavy chain comprises a nucleotide sequence of SEQ ID NO: 81, and the region that encodes the variable region of the light chain comprises a nucleotide sequence of SEQ ID NO: 83.

(14) The DNA according to (11) or (12), wherein a region that encodes the variable region of the heavy chain comprises a nucleotide sequence of SEQ ID NO: 114, and a region that encodes the variable region of the light chain comprises a nucleotide sequence of SEQ ID NO: 116.

(15) A recombinant vector, comprising the DNA according to any one of (11) to (14).

(16) A transformant, comprising the recombinant vector according to (15).

(17) A hybridoma which produces the monoclonal antibody according to any one of (1) to (10).

(18) A pharmaceutical composition, comprising the monoclonal antibody according to any one of (1) to (10).

(19) The pharmaceutical composition according to (18), which is a composition for cancer treatment.

(20) The pharmaceutical composition according to (19), wherein the composition for cancer treatment is a composition for treatment of one or two or more cancers selected from the group consisting of non-small cell lung cancer, pancreatic cancer and gastric cancer.

(21) The pharmaceutical composition according to any one of (18) to (20), wherein the monoclonal antibody is anchored on a surface of a liposome in which a toxin or an anti-cancer drug is encapsulated.

(22) A diagnostic reagent, which comprises the monoclonal antibody according to any one of (1) to (10).

(23) A polypeptide, having the properties of the following (a) and/or (b)

(a) having a reactivity to a cytoskeleton filament,

(b) causing no morphological change against normal cells, and causing a morphological change against cancer cells.

(24) A polypeptide, having the properties of the following (a) and/or (b)

(a) specifically recognizing a protein with a molecular weight of approximately 55 kDa that is derived from a human pancreatic cancer cell line PANC-1 and comprises an amino acid sequence of SEQ ID NO: 107;

(b) causing no morphological change against normal cells, and causing a morphological change against cancer cells.

(25) The polypeptide according to (24), wherein the protein with a molecular weight of approximately 55 kDa is vimentin.

(26) The polypeptide according to any one of (23) to (25), wherein the morphological change is a morphological change to one or more cell morphology selected from an axonal-like morphology, fibroblast-like morphology and neuronal cell-like morphology with neurites.

(27) The polypeptide according to any one of (23) to (26), wherein the polypeptide is the monoclonal antibody according to any one of (1) to (10).

(28) A pharmaceutical composition, comprising the polypeptide according to any one of (23) to (26).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram (photograph) showing a morphological change of each cell when HoAKs-1 antibody is added to cultured cancer cell lines. FIG. 1 depicts the cultured cancer cell line HLC-1 without (A) or with (B) HoAKs-1 antibody; the cultured cancer cell line PANC1 without (C) or with (D) HoAKs-1 antibody; the cultured cancer cell line MKN45 without (E) or with (F) HoAKs-1 antibody; and the cultured cancer cell line HUVECs without (G) or with (H) HoAKs-1 antibody.

FIG. 2 is a diagram showing anti-proliferative effects of the HoAKs-1 antibody on the cultured cancer cell lines HLC-1, MKN45, and HUVECs.

FIG. 3 is a diagram showing anti-proliferative effects of the HoAKs-1 antibody on the pancreatic cancer cell line PANC-1.

FIG. 4 is a diagram (photograph) showing the reactivity of the HoAKs-1 antibody to various tissue slices.

FIG. 5 is a diagram (photograph) showing the results of an analysis on an antigenic protein which the HoAKs-1 antibody recognizes.

FIG. 6 is a diagram (photograph) showing a morphological change of each cell when the HoAKs-1 antibody is removed from culture medium after allowing the antibody to act on the cultured cancer cell line for a certain period of time.

FIG. 7 is a diagram (photograph) showing the binding activity of the HoAKs-1 antibody to the surface of each living cancer cell. FIG. 7 depicts the cultured cancer cell line PANC1 with HoAKs-1 antibody (A) or with human IgM antibody (B); the cultured cancer cell line HLC-1 with HoAKs-1 antibody (C) or with human IgM antibody (D); and the cultured cancer cell line HUVECs with HoAKs-1 antibody (E) or with human IgM antibody (F).

FIG. 8 is a diagram (photograph) showing the binding activity of an anti-55 kDa mouse monoclonal antibody to the surface of each living cancer cell. FIG. 8 depicts the cultured cancer cell line PANC1 with antibody derived from the 2F6-1 cell line (A), with antibody derived from the 3F9-1 cell line (B), or with mouse IgM antibody (C); the cultured cancer cell line HLC-1 with antibody derived from the 2F6-1 cell line (D), with antibody derived from the 3F9-1 cell line (E), or with mouse IgM antibody (F); and the cultured cancer cell line HUVECs with antibody derived from the 2F6-1 cell line (G), with antibody derived from the 3F9-1 cell line (H), or with mouse IgM antibody (I).

FIG. 9 is a diagram (photograph) showing the binding activity of γ-HoA. antibody to the surface of each living cancer cell. FIG. 9 depicts the cultured cancer cell line PANC1 with FITC-conjugated anti-human Ig and γ-HoA. antibody (A) or with FITC-conjugated anti-human Ig (B); the cultured cancer cell line HLC-1 with FITC-conjugated anti-human Ig and γ-HoA. antibody (C) or with FITC-conjugated anti-human Ig (D); and the cultured cancer cell line HUVECs with FITC-conjugated anti-human Ig and γ-HoA. antibody (E) or with FITC-conjugated anti-human Ig (F).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described in detail.

<1> Monoclonal Antibody of the Present Invention

The monoclonal antibody of the present invention is a monoclonal antibody that specifically recognizes an antigenic protein shown in FIG. 5, which is derived from a human pancreatic cancer cell line PANC-1 (ATCC No. CRL1469) and has a molecular weight of approximately 55 kDa (a protein comprising an amino acid sequence of SEQ ID NO: 107). In addition, the antibody of the present invention is a monoclonal antibody which does not cause a morphological change in normal cells but cause a morphological change in cancer cells. Furthermore, the antibody of the present invention is a monoclonal antibody that specifically recognizes the protein shown in FIG. 5, that is derived from the human pancreatic cancer cell line PANC-1 and has a molecular weight of approximately 55 kDa (a protein comprising an amino acid sequence of SEQ ID NO: 107), and does not cause a morphological change in normal cells but cause a morphological change in cancer cells. As an antigenic protein of approximately 55 kDa, vimentin can be exemplified. In addition, the term “morphological change” refers to, for example, a morphological change from a normal morphology to an axonal-like morphology, fibroblast-like morphology and a neuronal cell-like morphology with neurites as shown in B and D of FIG. 1.

Specific examples of the monoclonal antibody of the present invention include antibodies in which variable region of the heavy chain comprises amino acid sequences of SEQ ID NOS: 86, 88 and 90 and variable region of the light chain comprises amino acid sequences of SEQ ID NOS: 92, 94 and 96. In the amino acid sequence of SEQ ID NO: 88, the amino acid at position 10 may be Cys or Tyr. In other words, there are two types of variable regions of the heavy chain, one having Cys at position 10 and the other having Tyr at position 10. In addition, the antibody of the present invention may have substitution, deletion, or addition of one or several amino acids in one or more of the above six kinds of sequences as far as the antibody has the specificity that it specifically recognizes the antigenic protein with molecular weight of approximately 55 kDa (a protein comprising an amino acid sequence of SEQ ID NO: 107) derived from the human pancreatic cancer cell line PANC-1. Here, the term “several” means preferably two to five, more preferably two to three, particularly preferably two.

The above six kinds of sequences are the sequences of the regions called as “hypervariable regions” in variable regions of the heavy and light chain. An antibody consists of heavy chains and light chains, and each of these chains is composed of a constant region and a variable region. A variable region comprises hypervariable regions which determine the specificity of immunoglobulin as an antibody and the binding affinity of the antibody to an epitope. Therefore, regions other than hypervariable regions may be derived from any of other antibodies, so far as hypervariable regions of the present invention comprise each of the above sequences. Here, the term “other antibodies” includes antibodies derived from organisms other than human, but antibodies of human origin are preferable in terms of reducing side effects.

In the present invention, a particularly preferable monoclonal antibody may be one comprising an amino acid sequence of SEQ ID NO: 82 in variable region of the heavy chain and an amino acid sequence of SEQ ID NO: 84 in variable region of the light chain, or one comprising an amino acid sequence of SEQ ID NO: 115 in variable region of the heavy chain and an amino acid sequence of SEQ ID NO: 117 in variable region of the light chain. Here, in the sequence of SEQ ID NO: 82 or 115, the combination of the amino acids at positions 14 and 51 may be either (Cys, Tyr) or (Tyr, Cys). In other words, there are two kinds of the sequences of variable region of the heavy chain, one having Cys at position 14 and Tyr at position 51 and the other having Tyr at position 14 and Cys at position 51. Furthermore, the sequence of SEQ ID NO: 84 or 117 may have Val or Ile at position 13. In other words, there are two kinds of the sequences of variable region of the heavy chain, one having Val at position 13 and the other having Ile at position 13.

In the present invention, the term “monoclonal antibody” refers to any of those including monoclonal antibodies and fragments thereof, F(ab′)₂ antibodies, F(ab′) antibodies, short-chain antibodies (scFv), diabodies, and minibodies. When the monoclonal antibody contains a constant region, amino acid sequences of its constant regions of the heavy and light chains are preferably one of those described in Nucleic Acids Research vol. 14, p1779, 1986; The Journal of Biological Chemistry vol. 257, p1516, 1982; and Cell vol. 22, p197, 1980. The antibody of the present invention comprising constant and variable regions may be, for example, one comprising an amino acid sequence of SEQ ID NO: 130 (heavy chain) and SEQ ID NO: 132 (light chain).

The monoclonal antibody of the present invention can be obtained by culturing a hybridoma producing the antibody of the present invention in a culture medium, for example, a RPMI1640 medium that contains fetal bovine serum. Alternatively, it can be obtained by preparing a gene (e.g., a gene comprising SEQ ID NO: 129 (heavy chain) or 131 (light chain)), in which a DNA encoding a constant region of heavy chain or light chain is ligated to a DNA encoding each variable region (e.g. DNA comprising SEQ ID NOS: 81 or 83), by means of a PCR method or a chemical synthesis; inserting the obtained gene into a conventionally-used expression vector (e.g., pcDNA3.1 (Invitrogen)) capable of expressing the gene; expressing the gene in a host cell such as a CHO cell (Chinese hamster ovary cell) or Escherichia coli to produce the antibody; and purifying the obtained antibody from the culture medium using a Protein A column or the like.

Furthermore, the monoclonal antibody of the present invention may be obtained by: preparing a hybridoma from an animal immunized with a protein of molecular weight of approximately 55 kDa that is derived from the human pancreatic cancer cell line PANC-1 and comprises an amino acid sequence of SEQ ID NO: 107, preferably vimentin (GenBank Accession No. M14144); culturing the hybridoma; and selecting a monoclonal antibody which can bind to a surface of living cancer cells from the obtained monoclonal antibodies. Examples of such a monoclonal antibody include those produced from hybridoma strains 2F6-1 and 3F9-1, which will be explained in the Examples described later.

<2> DNA of the Present Invention

The DNA of the present invention is a DNA that encodes the monoclonal antibody of the present invention. Examples thereof include a DNA that comprises a region encoding variable region of the heavy chain which comprises amino acid sequences of SEQ ID NOS: 86, 88 and 90; and a region encoding variable region of light chain which comprises amino acid sequences of SEQ ID NOS: 92, 94 and 96. Preferably, such a DNA comprises a region encoding variable region of the heavy chain which comprises nucleotide sequences of SEQ ID NOS: 85, 87 and 89; and a region encoding variable region of the light chain which comprises nucleotide sequences of SEQ ID NOS: 91, 93 and 95. Here, in the sequence of SEQ ID NO: 87, the nucleotide at position 29 may be either “a” or “g”. In other words, there are two types of the sequences encoding variable region of the heavy chain, one having “a” at position 29 and the other having “g” at position 29. Furthermore, in the sequence of SEQ ID NO: 95, the nucleotide at position 18 may be either “c” or “t”. In other words, there are two types of the sequences encoding variable region of the light chain, one having “c” at position 18 and the other having “t” at position 18.

The hypervariable regions encoded by those DNA sequences are regions that define the specificity of the antibody, so that sequences encoding the other regions may be those derived from other antibodies. Here, the term “other antibodies” includes antibodies derived from organisms other than human, but, antibodies of human origin are preferable in terms of reducing side effect.

In the present invention, particularly preferable DNA may be one comprising a sequence encoding an amino acid sequence of SEQ ID NO: 82 in variable region of the heavy chain and a sequence encoding an amino acid sequence of SEQ ID NO: 84 in variable region of the light chain, or one comprising a sequence encoding an amino acid sequence of SEQ ID NO: 115 in variable region of the heavy chain and a sequence encoding an amino acid sequence of SEQ ID NO: 117 in variable region of the light chain. Of those, a particularly preferable DNA may be one comprising a nucleotide sequence of SEQ ID NO: 81 encoding variable region of the heavy chain and a nucleotide sequence of SEQ ID NO: 83 encoding variable region of the light chain, or one comprising a nucleotide sequence of SEQ ID NO: 114 encoding variable region of the heavy chain and a nucleotide sequence of SEQ ID NO: 116 encoding variable region of the light chain. Here, in the sequence of SEQ ID NO: 81 or 114, the combination of the nucleotides at positions 41 and 152 may be either of (a, g) or (g, a). In other words, there are two types of the sequences encoding variable region of the heavy chain, one having “a” at position 41 and “g” at position 152 and the other having “g” at position 41 and “a” at position 152. Furthermore, in the sequence of SEQ ID NO: 83 or 116, the combination of the nucleotides at positions 37, 183 and 258 may be any of (a, a, t), (a, a, c), and (g, g, t). In other words, there are three types of the sequences encoding variable region of the light chain, one having “a” at position 37, “a” at position 183 and “t” at position 258, one having “a” at position 37, “a” at position 183 and “c” at position 258, and one having “g” at position 37, “g” at position 183, and “t” at position 258.

Furthermore, the DNA of the present invention may be one which is capable of hybridizing with a DNA comprising nucleotide sequences of SEQ ID NOS: 81 and 83, or with a DNA comprising nucleotide sequence of SEQ ID NOS: 114 and 116 under stringent conditions as far as it encodes a monoclonal antibody that specifically recognizes an antigenic protein with a molecular weight of approximately 55 kDa that is derived from the human pancreatic cancer cell line PANC-1 (a protein comprising an amino acid sequence of SEQ ID NO: 107). Here, stringent conditions include those under which hybridization is performed at a salt concentration corresponding to 60° C., 1×SSC, 0.1% SDS, preferably 0.1×SSC, 0.1% SDS, which corresponds to washing conditions in Southern hybridization.

The DNA of the present invention may be one that encodes all of the constant region and variable region of heavy and light chains. Alternatively, it may be one encoding only the variable regions of the heavy and light chains. When the DNA encodes all of the constant region and variable region, the nucleotide sequences of the constant regions of the heavy and light chains are preferably those described in Nucleic Acids Research vol. 14, p1779, 1986, The Journal of Biological Chemistry vol. 257, p1516, 1982, and Cell vol. 22, p197, 1980. The DNA of the present invention, which encodes the constant region and variable region, encompasses a DNA comprising a nucleotide sequence of SEQ ID NO: 129 (heavy chain) and a nucleotide sequence of SEQ ID NO: 131 (light chain).

The DNA of the present invention can be obtained by the method described below. At first, total RNA is prepared from the cells (e.g., hybridoma cells) of the present invention using a commercially-available RNA extraction kit and then cDNA is synthesized from the total RNA by reverse transcriptase using random primers and the like. Subsequently, using the PCR method in which oligonucleotides each having a sequence conserved in a variable region of heavy chain or light chain of human antibody are used as primers, cDNA encoding such an antibody is amplified. The sequence encoding the constant region can be obtained by amplification of the known sequence by the PCR method. The nucleotide sequence of the DNA can be determined by a conventional method after inserting the DNA into a plasmid for sequence determination.

Furthermore, the present invention provides a recombinant vector comprising the DNA of the present invention, and a transformant containing the recombinant vector. The recombinant vector may be a vector which can be used for gene expression in prokaryotic cells such as Escherichia coli (e.g., pBR322, pUC119 or a derivative thereof), preferable is a vector which can be used for gene expression in eukaryotic cells, and more preferable is a vector which can be used for gene expression in cells derived from a mammal. Examples of the vectors which can be used for gene expression in cells derived from a mammal include a plasmid vector such as pcDNA3.1 (manufactured by Invitrogen Co., Ltd.) and a virus vector such as pDON-AI DNA (manufactured by TAKARA BIO INC.). The transformant to be introduced with the recombinant vector of the present invention may be a prokaryotic cell such as Escherichia coli, but preferable is a eukaryotic cell, and more preferable is a cell derived from a mammal. Examples of the cells derived from a mammal include a Chinese hamster ovary cell (CHO cell).

<3> Hybridoma of the Present Invention

The hybridoma of the present invention is a hybridoma that produces the monoclonal antibody as described above. Examples of the hybridomas of the present invention include hybridoma strains HoAKs-1, 2F6-1 and 3F9-1, which will be explained in the Examples described later. The hybridoma of the present invention can be obtained by the following method. At first, on the basis of the method of A. Imam et. al (Cancer Research vol. 45, 263, 1985), tumor-infiltrating lymphocytes are isolated from the tumor tissue removed from a patient diagnosed with lung cancer and then the cells containing the lymphocytes are fused with mouse myeloma cells using polyethylene glycol to obtain hybridoma cells. Subsequently, enzyme immunoassay is carried out using the supernatant of the obtained hybridoma and then the hybridoma cells that produce antibodies that positively react to various cancer cell lines fixed with paraformaldehyde are selected, followed by cloning the obtained hybridomas by limiting dilution. Alternatively, the hybridoma of the present invention can be also obtained by immunizing a mouse using a protein with a molecular weight of approximately 55 kDa derived from the human pancreatic cancer cell line PANC-1 (a protein comprising the amino acid sequence of SEQ ID NO: 107) shown in FIG. 5 and then fusing the resulting lymphocytes with mouse myeloma cells.

<4> Pharmaceutical Composition of the Present Invention

The pharmaceutical composition OF THE PRESENT INVENTION comprises the monoclonal antibody of the present invention together with a pharmaceutically acceptable carrier. Examples of the pharmaceutically-acceptable carriers include soluble carriers such as known buffers which can be physiologically acceptable (e.g., phosphate buffer) or solid-state carriers such as latex beads.

The pharmaceutical composition OF THE PRESENT INVENTION is suitably used as a therapeutic agent for cancer, particularly for non-small cell lung cancer, pancreatic cancer, and gastric cancer. In addition, the pharmaceutical composition of the present invention may be a composition using the cell-killing effect and anti-proliferative effect of the monoclonal antibody itself, or may be a composition for targeting an anti-cancer drug such as adriamycine to a cancer tissue by binding the anti-cancer drug to the monoclonal antibody of the present invention.

In the present invention, a particularly suitable pharmaceutical composition is one in which the antibody of the present invention is anchored on a liposome containing a toxin, an anti-cancer drug or the like. The liposome used for anchoring the antibody may be composed of a lipid bilayer. Alternatively, the liposome used may be composed of a multiple lipid layers or composed of a single lipid layer. Examples of the constituents of the liposome include phosphatidylcholine, cholesterol and phosphatidyl ethanolamine, and further include phosphatidic acid as a substance for imparting the liposome with electric charge. The ratio of those constituents is, for example, 0.3 to 1 mol, preferably 0.4 to 0.6 mol of cholesterol, 0.01 to 0.2 mol, preferably 0.02 to 0.1 mol of phosphatidylethanolamine, and 0 to 0.4 mol, preferably 0 to 0.15 mol of phosphatidic acid per 1 mol of phosphatidylcholine.

A method of producing the liposome may be any of conventional methods. For instance, it can be produced using a method (Biochimica et Biophysica Acta vol. 812, p55, 1985) in which a mixture of the lipids, from which a solvent has been removed, is emulsified by a homogenizer or the like and then subjected to freeze-thawing to obtain a multilamellar liposome, followed by adjustment of pore size of the liposome appropriately by ultrasonication, high-speed homogenization, or pressure filtration through a membrane having uniform-size pores. Preferably, the liposome has a particle size of 30 to 200 nm.

Examples of the pharmaceutical agents to be encapsulated in the liposome include: carcinostatic agents such as adriamycin, daunomycin, mitomycin, cisplatin, vincristine, epirubicin, methotrexate, 5-Fu (5-Fluorouracil) and aclacinomycin; toxins such as ricin A and diphtheria toxin; and antisense RNA. Encapsulation of the agent into liposome may be accomplished by hydration of the lipids with an aqueous solution of the agent. In addition, adriamycin, daunomycin and epirubicin may be encapsulated into the liposome by a remote-loading method using pH gradient (Cancer Res. vol. 49 p5922, 1989).

Examples of methods of anchoring the monoclonal antibody on the surface of the liposome include a method in which a purified antibody is coupled with a hydrophobic substance for anchoring the antibody on the liposome, and a method in which an antibody is cross-linked to phosphatidyl ethanolamine using glutaraldehyde. More preferable method is a method in which a liposome containing a lipid into which a maleimide group has been introduced is prepared and an anti-cancer agent or toxin is encapsulated therein, and allowing it to react with a thiolated antibody to thereby anchor the antibody on the surface of the liposome. In addition, a water-soluble polymer derivative that contains a reactive site for an amino group, and a thiol- or intrinsic thiol-group moiety can be preferably used (JP 11-152234A). On the other hand, the surface of the liposome may be modified by allowing the remaining maleimide group to react with a thiolated polyalkylene glycol moiety.

Examples of the methods for introducing a thiol-group into the antibody include a method employing N-succinimidyl-3-(2-pyridyldithio)propionate (SPDP) or compounds such as iminothiolane and mercaptoalkylimidate, which is usually used for thiolation of protein, for introducing a thiol-group to the amino group of the antibody, or a method in which an intrinsic dithiol group of the antibody is reduced to form a thiol group. The method using an intrinsic thiol group is preferable from the view point of maintaining the activity of the antibody. Furthermore, the antibody may be treated with an enzyme such as pepsin to form F(ab′)₂ and then reduced with dithiothreitol (DTT) and the like to form F(ab′), which provides one to three thiol groups for binding to the liposome. The binding of the thiolated antibody to the maleimide group-containing liposome may be accomplished by reacting them in a neutral buffer at pH 6.5 to 7.5 for 2 to 16 hours.

The pharmaceutical for cancer treatment of the present invention may be formulated by any of conventional methods such as a dehydration method (JP02-502348A), a method in which a stabilizing agent to obtain a liquid formulation is added (JP64-9331A), and a lyophilization method (JP64-9931A). The pharmaceutical for cancer treatment of the present invention may be administered in intravascularly, intraperitoneally and the like, as local administrations. The dosage thereof can be optimized for the respective drugs encapsulated into the liposome. When the agent is adriamycin, the dosage of adriamycin is 50 mg/kg or less, preferably 10 mg/kg or less, and more preferably 5 mg/kg or less.

<5> Diagnostic Reagent of the Present Invention

Examples of the diagnostic reagents of the present invention include those taking advantage of the specificity of the antibody of the present invention against cancer cells, particularly a cancer diagnostic reagent comprising the antibody of the present invention, a secondary antibody, a detection substrate, and other components.

<6> Polypeptide of the Present Invention

The polypeptide of the present invention includes a polypeptide that specifically recognize a protein with molecular weight of approximately 55 kDa (a protein comprising an amino acid sequence of SEQ ID NO: 107), that is derived from a human pancreatic cancer cell line PANC-1 shown in FIG. 5. In addition, it includes a polypeptide which does not cause a morphological change in a normal cell but cause a morphological change in a cancer cell. Furthermore, it may be a polypeptide that specifically recognizes a protein with a molecular weight of approximately 55 kDa (a protein comprising an amino acid sequence of SEQ ID NO: 107) that is derived from the human pancreatic cancer cell line PANC-1 shown in FIG. 5, and does not cause a morphological change in a normal cell but cause a morphological change in a cancer cell. As the antigenic protein of approximately 55 kDa, vimentin can be exemplified. In addition, the term “morphological change” refers to, for example, the morphological change from a normal cell morphology into an axonal-like morphology, fibroblast-like morphology or a neuronal cell-like morphology with neurites as shown in B and C in FIG. 1.

Specific examples of the polypeptides of the present invention include a polypeptide which is adsorbed on PROSEP-A as explained in the Examples described later. More preferably, the monoclonal antibody of the present invention is included. The polypeptide of the present invention causes a morphological change specifically to cancer cells, so that it can be used for the manufacture of a pharmaceutical composition, particularly for treatment of cancers, such as non-small cell lung cancer, pancreatic cancer and gastric cancer.

EXAMPLES

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples without departing from the scope of the present invention.

(1) Preparation of Hybridomas by Cell Fusion Between Infiltrating Lymphocytes from a Cancer Patient and Mouse Myeloma Cells

(1)-1: Preparation of Lymphocytes

A tumor tissue removed from a patient with lung cancer was cut into small masses with a scalpel, and then well suspended in a culture medium A (RPMI1640+50 μg/ml gentamicin sulfate), and the culture medium was collected (named as medium (I)). The small masses of the tumor tissue were further cut into fine pieces with a razor edge, and then cells were dispersed in fresh culture medium A by passing through a pipette. This cell suspension was centrifuged at 1,000 rpm for 5 minutes and the supernatant was collected (named as supernatant II). The medium (I) was mixed with the supernatant (II) and the mixture was centrifuged at 3,000 rpm for 5 minutes, and thereby approximately 4×10⁷ cells containing tumor-infiltrating lymphocytes were obtained.

(1)-2: Cell Fusion

The cells containing tumor-infiltrating lymphocytes were fused to mouse myeloma cells (approximately 4×10⁷ cells) using polyethylene glycol 1500 (Roche Diagnostics) according to a standard method (Cancer Research vol. 45, 263, 1985). The fused cells were suspended in a culture medium B (culture medium A supplemented with 10% fetal bovine serum (FCS)) so that the cell density becomes 5×10⁵ cells/ml. The suspension was dispensed on a 96-well plate at 100 μl/well and cultured at 37° C. in CO₂ incubator. On the second day, the culture medium B supplemented with 10 μM hypoxanthine, 0.04 μM aminopterin and 1.6 μM thymidine (culture medium B supplemented with HAT) was added to the wells at 100 μl/well and cultured until colonies of hybridomas appeared. As a result, colonies of hybridomas appeared in 10 wells.

(2) Evaluation of Reactivity of Human Monoclonal Antibody to Cancer Cell Lines

(2)-1: Cancer Cell Line and its Maintenance

Using the culture supernatant of the obtained hybridomas, reactivity to fixed cancer cell lines including: a lung cancer cell line HLC-1 (Cancer vol. 67, No. 4, pp483-492, 1976; provided from Mr. Suzuki in the Medical Department of the Keio University); a gastric cancer cell line MKN45 (Japanese Journal of Cancer and Chemotherapy, vol. 5, p89, 1978; provided from IBL Co., Ltd.), and a pancreatic cancer cell line SUIT2 (provided from Mr. Iguchi in National Kyushu Cancer Center) was tested to select a hybridoma of interest. Those cancer cell lines were maintained and grown at 37° C. under 5% CO₂ in a culture medium D that was prepared by supplementing 5% FCS to culture medium C (D-MEM/F12+50 μg/ml gentamicin sulfate).

(2)-2: Measurement of Reactivity to Cancer Cell Lines

The above-described cancer cell lines were respectively cultured in a 96-well plate for 3 to 4 days until becoming a monolayer. After the supernatant was removed, the plate was washed once with 10 mM phosphate buffer (pH 7.4, 0.15 M NaCl: PBS) and fixed with 2% paraformaldehyde at room temperature for 20 minutes. After washing five times with PBS, the plate was added and blocked with 150 μl/well of PBS solution containing 5% BSA (bovine serum albumin). Then, the plate was washed five times with PBS and supplemented with 50 μl of the hybridoma culture supernatant to react at 37° C. for one and half hours. Next, the plate was washed five times with PBS and then added with 50 μl of a horseradish peroxidase-conjugated goat antibody against a human antibody (CAPPEL; 1,000-fold dilution) to react at 37° C. for 1 hour. Subsequently, the plate was washed with PBS containing 0.05% of Tween 20 (PBS-T) and then added with 50 μl/well of phosphate-citrate buffer containing o-phenylenediamine dihydrochloride (5.2%) and H₂O₂ (0.015%). Reaction was conducted at room temperature until color development was observed, followed by the measurement of absorbance at 490 nm with a microphotometer (Nihon Intermed). Cloning of hybridoma was conducted by limiting dilution of the cells obtained from the wells in which reactivity was detected, and thereby a hybridoma cell line HoAKs-1 was obtained. Hereinafter, a monoclonal antibody obtained from this cell line is referred to as a HoAKs-1 antibody.

(3) Purification and Labeling of HoAKs-1 Monoclonal Antibody

(3)-1: Culture of Hybridoma HoAKs-1 and Purification of HoAKs-1 Monoclonal Antibody

At first, fetal bovine serum was allowed to pass through a protein A-glass bead column (PROSEP-A) (bio PROCESSING) to prepare a serum from which substances adsorbed in the PROSEP-A were removed. The culture medium A supplemented with 7 to 10% of this serum was used to culture the hybridoma HoAKs-1. Next, the culture medium in which the hybridoma HoAKs-1 had been cultured was loaded onto the PROSEP-A to thereby adsorb a PROSEP-A-adsorbed polypeptide, which was then eluted to purify the PROSEP-A-adsorbed polypeptide. This PROSEP-A-adsorbed polypeptide was used as a HoAKs-1 antibody in the subsequent procedures. It was considered that the use of the above-described serum in culture enabled to provide the purified HoAKs-1 antibody with no contamination of substances adsorbed in the PROSEP-A such as antibodies derived from serum. The HoAKs-1 antibody was confirmed to be pure IgM by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (data not shown).

(3)-2: Biotinylation of HoAKs-1 Antibody

After the HoAKs-1 antibody purified with the PROSEP-A was biotinylated with a biotinylation reagent (Amersham Biosciences) according to the manufacturer's instructions, the labeled antibody was separated from free biotin by gel filtration method.

(4) Analysis of Effects on Living Cancer Cell Lines and Vascular Endothelial Cells

(4)-1: Cancer Cell Lines and Vascular Endothelial Cells and their Maintenance

A lung cancer cell line HLC-1, a gastric cancer cell line MKN45, and a pancreatic cancer cell line PANC-1 (ATCC No. CRL1469) as human cancer cell lines and vascular endothelial cells HUVECs (DAINIPPON PHARMACEUTICAL Co., Ltd.) as a normal human cell were used. Those cancer cell lines were cultured and grown in the culture medium D at 37° C. under 5% CO₂. The human vascular endothelial cell HUVECs was cultured and grown using CS-C culture medium (Cell SYSTEMS).

(4)-2: Analysis of Effects on Morphology of Cancer Cell Lines and Vascular Endothelial Cells

The HoAKs-1 antibody was sterilized by filtration. The resulting HoAKs-1 antibody was diluted with the culture medium C or the CS-C culture medium to have a concentration of approximately 140 μg/ml, and dispensed into a 96-well plate at 100 μl/well. Next, each of the cultured cancer cells and vascular endothelial cell HUVECs was diluted to a density of 3×10⁴ cells/ml with the culture medium C or the CSC-culture medium containing 10% human serum (ICN Biomedicals). The cell suspension was dispensed on a plate at 100 μl/well so that the number of cells in each well became 1.5×10³ cells/well and the concentration of the HoAKs-1 antibody became approximately 70 μg/ml. The plate was incubated at 37° C. under 5% CO₂. The culture supernatant was changed by the same medium as described above once every other day, three times in total. On the sixth day, morphological changes of the cells were observed under a light microscope.

The result of observation is shown in FIG. 1. No cytomorphological change by the addition of the antibody was observed in the vascular endothelial cells HUVECs as a normal cell (FIGS. 1-G and 1-H), while remarkable morphological changes by the addition of the antibody were observed in the lung cancer cell line HLC-1 (FIGS. 1-A and 1-B) and the pancreatic cancer cell line PANC-1 (FIGS. 1-C and 1-D). Those cells were changed into axon-like morphology, fibroblast-like morphology, or neuronal cell-like morphology with protrusion. Especially, the pancreatic cancer cell line PANC-1 exhibited morphological changes similar to those observed in starved condition. Moreover, slight morphological changes were observed in the gastric cancer cell line MKN45 (FIGS. 1-E and 1-F). From the above observations, the possibility that the HoAKs-1 antibody had some effects on the cancer cell lines was suggested.

(4)-3: Analysis of Anti-Proliferative Effect on Cancer Cell Lines

The lung cancer cell line HLC-1 and the gastric cancer cell line MKN45 in which morphological changes had been observed and the vascular endothelial cell HUVECs as a normal cell in which no morphological change had been observed were seeded on a 96-well plate under the same conditions, and cultured at 37° C. under 5% CO₂ in the presence of approximately 70 μg/ml of the HoAKs-1 antibody; the culture supernatant was changed by the same medium as described above once every other day, three times in total; and on the 6th day, the number of living cancer cells was compared by MTT assay (J. Immunol. Methods vol. 70, p257, 1984). As a control, human antibody IgM (CHEMICON) was used to conduct the same experiment.

The result is shown in FIG. 2. When the number of cells under control conditions without the addition of the antibody was defined as 100%, approximately 60% and approximately 50% anti-proliferative effects were observed in the lung cancer cell line HLC-1 and the gastric cancer cell line MKN45, respectively, by the addition of the HoAKs-1 antibody. On the other hand, no difference was observed in the vascular endothelial cell HUVECs. Moreover, no anti-proliferative effect on the cancer cell lines by the addition of the antibody was observed when the human IgM was used as a control.

The cancer cell line PANC-1 in which morphological changes had been observed was seeded on a 96-well plate at 1×10³ cells/well and cultured at 37° C. under 5% CO₂ in the presence of 300 μg/ml, 100 μg/ml or 30 μg/ml of the HoAKs-1 antibody, respectively. The culture supernatant was changed by the same medium as described above once every other day, three times in total. On the 6th day, the number of living cancer cells was compared using a bromodeoxyuridin (BrdU) cell proliferation assay kit (Oncogene). On the 6th day, the BrdU solution was added to each well according to the instructions of the kit and cells were cultured overnight, and the amount of BrdU uptaken by the living cancer cells was measured on the 7th day. For control, human IgM was used to conduct the same experiment.

The result is shown in FIG. 3. The amount of BrdU uptaken under control conditions without the addition of the antibody was indicated by 100%. It was confirmed that the proliferation of the pancreatic cancer cell line PANC-1 was suppressed in a concentration-dependent manner by the HoAKs-1 antibody. No anti-proliferative effect on the cancer cell lines by the addition of the antibody was observed when the IgM was used as a control.

(5) Analysis of Reactivity to Various Tissue Sections

(5)-1: Preparation of Various Tissue Sections

Lung cancer tissue sections from which the lymphocytes used for preparation of the HoAKs-1-producing hybridoma had been derived, and noncancerous lung tissue sections surrounding the same cancer tissue were fixed in formalin solution according to a standard method and embedded in paraffin to prepare tissue sections. In addition, various cancer cell lines (lung cancer cell lines: HLC-1 (Keio University), A549 and PC9 (IBL); pancreatic cancer cell lines: SUIT2 (Kyushu Cancer Center), PANC-1 and PK8 (the Cell Resource Center for Biomedical Research; the Institute of Development, Aging and Cancer of the Tohoku University); gastric cancer cell lines: MKN45, MKN74, and HSC-3 (all of which from IBL Co., Ltd.); and colon cancer cell lines: HT29 (ATCC No. HTB38), DLD-1 (ATCC No. CCL221), LoVo (ATCC No. CCL229), and COLO205 (ATCC No. CCL222)) were respectively grown in the culture medium D at 37° C. under 5% CO₂ and transplanted at approximately 1×10⁶ to 1×10⁷ cells subcutaneously in nude mice (CLEA Japan, Inc.) to form tumors. The formed tumors were extracted and tumor tissue sections were prepared in the same way as described above.

(5)-2: Detection of Reactivity to Various Tissue Sections

After the prepared various tissue sections were subjected to deparaffinization and blocking procedures according to a standard method, the resulting tissue sections were reacted with the biotinylated HoAKs-1 antibody described in Example (3)-2. DAKO Catalyzed Signal Amplification (CSA) System (DAKO) was used for detection, and reactivity was detected as reddish brown stain by diaminobenzidine. For the immunostained tissue sections, cell nuclei in the tissues were stained in blue with hematoxylin in order to obtain tissue images.

The stained images of various tumor tissue sections in which reactivity was observed and tissue sections from the autologous lung noncancerous portion are shown in FIG. 4. It was found that the HoAKs-1 antibody exhibits strong reactivity to the tumor cells in the tissue sections of autologous lung-cancer from which the hybridoma had been derived, and against the tumor cells formed in the nude mice including lung cancer cell line-mediated tumors such as HLC-1 and A549, the pancreatic cancer cell line-mediated tumors such as SUIT2, PANC-1 and PK-8, and the gastric cancer cell line-mediated tumor such as MKN45. On the other hand, no reactivity was observed against the tissue sections from the noncancerous portion.

Although not shown in FIG. 4, staining was also conducted in the same procedures as described above by using, as a control, a human antibody purified from human serum with the PROSEP-A column in the same way as the HoAKs-1 or by using an IgM-type human monoclonal antibody A having the same subtype as the HoAKs-1 antibody, which was obtained in the same way. Those antibodies had no reactivity to the insoluble fraction of the PANC-1 cell as described below nor specific reactivity to each of the tissue sections as described above.

(6) Analysis of an Antigen Recognized by HoAKs-1 Antibody

(6)-1: Preparation of Antigen Sample from Cancer Cell Line

Using proteins derived from the pancreatic cancer cell line PANC-1 that showed remarkable morphological changes and was confirmed to have reactivity to the antibody in the tumor formed by transplanting the cell line in the nude mouse, substances with which the HoAKs-1 antibody reacted was identified by Western blotting. The pancreatic cancer cell line PANC-1 was grown in a flask at 37° C. under 5% CO₂. The culture supernatant in the flask was removed and the cells were washed once with PBS. A small amount of PBS was then added to the flask and the cells were removed with a cell scraper and transferred to a centrifuge tube, followed by the collection of the cells by centrifugation at 1,000 rpm for 5 minutes. After washing twice with PBS, TNE-buffer (10 mM Tris-HCL (pH 7.6), 150 mM NaCl, 1 mM EDTA) containing protease inhibitor (5 μg/ml leupeptin, 5 μg/ml pepstatin A, 5 μg/ml chymostatin (all of which from PEPTIDE INSTITUTE, Inc.)) was added in an amount (v/v) 10 times the amount of the collected cells. The cells were disrupted under ice-cooling condition using a glass homogenizer and centrifuged at 10,000 g for 20 minutes, and thereby soluble supernatant fraction and insoluble precipitates were obtained. The precipitates were suspended by the addition of RIPA-buffer (50 mM Tris-HCL (pH 8.0), 150 mM NaCl, 1% Nonidet P-40, 0.5% deoxycholic acid, 0.1% SDS) containing protease inhibitor (5 μg/ml leupeptin, 5 μg/ml pepstatin A, 5 μg/ml chymostatin) in the same volume as the volume of the previously added TNE-buffer, and subjected to ultrasonic homogenization for about 3 minutes to disperse the precipitates.

(6)-2: Analysis by Western Blotting

Approximately 20 μg of each of the proteins from the above-described soluble fraction and the proteins from insoluble fraction solubilized with the RIPA buffer that were both derived from the PANC-1 was used to perform electrophoresis on 2 to 15% acrylamide gradient gel. After electrophoresis, the proteins were transferred from the gel to a PVDF membrane. After the PVDF membrane was blocked, the membrane was reacted with HoAKs-1 antibody over night at 4° C. and subsequently at 37° C. for 1 hour. Then, the PVDF membrane was washed with PBS-T and added with a horseradish peroxidase (HRP)-conjugated goat antibody against a human antibody (1,000-fold dilution, CAPPEL) to react at 37° C. for 1 hour. Next, the PVDF membrane was washed with PBS-T and substances that reacted with the HoAKs-1 were detected with Western blotting luminol reagent (Santa Cruz Biotechnology).

The electrophoretic pattern of the proteins derived from the PANC-1 cell (Coomassie Brilliant Blue staining) and the result of Western blotting are shown in FIG. 5. It was found that the HoAKs-1 antibody exhibited reactivity to a single protein of approximately 55 kDa from the insoluble fraction (membrane fraction) of the homogenate of the pancreatic cancer cell line PANC-1.

(6)-3: Amino Acid Sequencing Analysis

Approximately 560 μg of the above-described insoluble fraction derived from PANC-1 was solubilized with the RIPA buffer and treated with Amersham Plus One 2-D Clean-Up kit, and then approximately 40 μg of the sample was subjected to two-dimensional electrophoresis. In the first dimension of electrophoresis, the sample was penetrated into ZOOM STRIP (pH 3-10NL) (Invitrogen) to carry out isoelectric focusing. In the second dimension, 10% acrylamide gel was used to carry out SDS-electrophoresis. Substance that reacted with HoAKs-1 was detected on the two-dimensional electrophoretic pattern in the same way as the above-described Western blotting. The two-dimensional electrophoresis was repeated thirteen times using the same kind of sample. The gel after electrophoresis was stained with Coomassie Brilliant Blue and 13 spots corresponding to the reactants of the HoAKs-1 antibody detected in the Western blotting were excised from the gel.

The excised gel sections were washed and added with Tris buffer (pH 8.5) containing lysyl-end peptidase to conduct overnight treatment at 35° C. Thereafter, the solution was subjected to reversed phase HPLC (TSKgel ODS-80Ts) to separate peptide fragments. Of the separated peptides, the fraction No. 58 was loaded onto the amino acid sequence analyzer (Procise 494 HT Protein Sequencing System), and thereby a peptide sequence from Val at its N terminal up to the twelfth residue was determined among mainly detected amino acid sequences. That sequence was VELQELNDRFAN (SEQ ID NO: 107) and found to conform to the internal sequences of various kinds of vimentins (Mol. Cell. Biol. Vol. 6, p3614-3620, 1986, GenBank Accession No. M14144) and desmins (Gene vol. 78, p243-254, 1989) as a result of homology research. Because vimentin and desmin are cytoskeletal filaments, the HoAKs-1 antibody was considered to be an antibody having reactivity to cytoskeletal filaments.

It was considered that the HoAKs-1 antibody exhibits morphological changes (FIG. 1) and anti-proliferative effects (FIGS. 2 and 3) on the tumor cells via a protein containing this amino acid sequence VELQELNDRFAN (SEQ ID NO: 107). Because the tumor cells exhibit morphological changes by adding the HoAKs-1 antibody in culture medium, this antigenic protein was predicted to exist on the membrane surface of the tumor cells.

(7) Cloning of a Gene Encoding Human Monoclonal Antibody HoAKs-1 and Determination of its Nucleotide Sequence

Total RNA was prepared from the HoAKs-1 antibody-producing hybridoma using an RNeasy™ Protect Mini kit (QIAGEN). Reverse transcription reaction was performed using RNA PCR KIT (AMV) (TAKARA BIO INC.) and random 9mers as primers to synthesize cDNAs.

Based on the known sequence of a gene encoding antibody (J Mol Biol. vol. 222, pp581-597, 1991), for amplifying variable region of the heavy chain, a mixture of equal amounts of PCR primers (5′ end-primers) including VH1 (SEQ ID NO: 1), VH2 (SEQ ID NO: 3), VH3 (SEQ ID NO: 5), VH4 (SEQ ID NO: 7), VH5 (SEQ ID NO: 9) and VH6 (SEQ ID NO: 11) each corresponding to the N-terminal amino acid sequences (SEQ ID NOS: 2, 4, 6, 8, 10 and 12) conserved in the frame 1 of variable region of the heavy chain of human antibodies and a mixture of equal amounts of PCR primers (3′ end-primers) including JH1 (SEQ ID NO: 13), JH2 (SEQ ID NO: 15), JH3 (SEQ ID NO: 17) and JH4 (SEQ ID NO: 19) each corresponding to the C-terminal amino acid sequences (SEQ ID NOS:14, 16, 18 and 20) conserved in the frame 4 of variable region of the heavy chain of human antibodies were used as primers for PCR amplification.

A mixture of equal amounts of PCR primers (5′ end-primers) including VK1 (SEQ ID NO: 21), VK2 (SEQ ID NO: 23), VK3 (SEQ ID NO: 25), VK4 (SEQ ID NO: 27), VK5 (SEQ ID NO: 29) and VK6 (SEQ ID NO: 31) each corresponding to the N-terminal amino acid sequences (SEQ ID NOS: 22, 24, 26, 28, 30, and 32) conserved in the frame 1 of variable region of κ chain of human antibodies and a mixture of equal amounts of PCR primers (3′ end-primers) including JK1 (SEQ ID NO: 33), JK2 (SEQ ID NO: 35), JK3 (SEQ ID NO: 37), JK4 (SEQ ID NO: 39) and JK5 (SEQ ID NO: 41) each corresponding to the C-terminal amino acid sequences (SEQ ID NOS: 34, 36, 38, 40 and 42) conserved in the frame 4 of variable region of κ chain of human antibodies were used as primers for amplifying variable region of the κ chain.

A mixture of equal amounts of PCR primers (5′ end-primers) including VL1 (SEQ ID NO: 43), VL2 (SEQ ID NO: 45), VL3 (SEQ ID NO: 47), VL4 (SEQ ID NO: 49), VL5 (SEQ ID NO: 51), VL6 (SEQ ID NO: 53) and VL7 (SEQ ID NO: 55) each corresponding to the N-terminal amino acid sequences (SEQ ID NOS: 44, 46, 48, 50, 52, 54 and 56) conserved in the frame 1 of variable region of λ chain of human antibodies and a mixture of equal amounts of PCR primers (3′ end-primers) including JL1 (SEQ ID NO: 57), JL2 (SEQ ID NO: 59) and JL3 (SEQ ID NO: 61) each corresponding to the C-terminal amino acid sequences (SEQ ID NOS: 58, 60 and 62) conserved in the frame 4 of variable region of λ chain of human antibodies were used as primers for amplifying variable region of the λ chain.

PCR reaction was performed using Perkin Elmer Gene Amp PCR System 2400 and RNA PCR KIT (AMV) (TAKARA BIO INC.) according to the manufacturer's instructions. As a result, the light chain was amplified by PCR with the primers for the K chain but not amplified with the primers for the λ chain. Therefore, it was revealed that the light chain of the antibody produced by the hybridoma was a κ chain.

The amplified DNA fragments each encoding variable region of the heavy or light chain were purified using MinElute™ PCR Purification kit (QIAGEN). Next, using TOPO™ TA cloning kit (Invitrogen), the purified PCR products were ligated to pCR™2.1-TOPO™ cloning vector, and the obtained plasmids were used to transform E. coli. Appeared colonies were picked up and plasmids were isolated using QIAGEN Plasmid mini kit (QIAGEN), followed by digestion with EcoRI at 37° C. for 15 minutes and electrophoresis on 2% agarose gel to confirm the insertion of a DNA fragment of interest.

The nucleotide sequences of the inserted DNA fragments were analyzed for several colonies by CEQ 2000 DNA Analysis System (Beckman) using M13 primers. As a result, four sequences including HO9 (SEQ ID NO: 63), H12 (SEQ ID NO: 65), H27 (SEQ ID NO: 67) and H30 (SEQ ID NO: 69) were identified from the analysis of the heavy chain. Ten sequences including K30 (SEQ ID NO: 71), K31 (SEQ ID NO: 73), K32 (SEQ ID NO: 75), K35 (SEQ ID NO: 77), K39 (SEQ ID NO: 79), KMO5 (SEQ ID NO: 97), KMO6 (SEQ ID NO: 99), KMO26 (SEQ ID NO: 101), KMO36 (SEQ ID NO: 103) and KMO40 (SEQ ID NO: 105) were identified from the analysis of the κ chain. Of those sequences, HO9, H12, H27, H30, K30, K31, K32, K35 and K39 were considered to encode heavy and light chains of human antibody. By comparing those nucleotide sequences and the corresponding amino acid sequences (heavy chain: SEQ ID NOS: 64, 66 and 68; κ chain: SEQ ID NOS: 70, 72, 74, 76, 78 and 80), the nucleotide sequences of the variable regions (heavy chain: SEQ ID NO: 81; light chain: SEQ ID NO: 83) and the amino acid sequences (heavy chain: SEQ ID NO: 82; light chain: SEQ ID NO: 84) were determined for each of the heavy and light chains.

For the gene encoding HoAKs-1 antibody, a sequence of the 3′-region relative to the above-determined sequence was further determined. The amplification of the 3′-region of the heavy-chain gene was carried out by PCR using a 5′-side primer of primer VH3 (SEQ ID NO: 5) corresponding to the N-terminal amino acid sequence conserved in the frame 1 of variable region of the heavy chain of human antibodies, and a 3′-side primer of PCR primer IgMFOR (SEQ ID NO: 108) corresponding to the amino acid sequence of constant region of the heavy chain of human antibodies. The resulting PCR product was inserted into a plasmid in the same way as described above to determine the nucleotide sequence. As a result, a sequence composed of 57 nucleotides (SEQ ID NO: 110) which follows the above-described nucleotide sequence of variable region of the heavy chain (SEQ ID NO: 81) was determined. This nucleotide sequence was predicted to encode 19 amino acids (SEQ ID NO: 111). The nucleotide sequence of a gene encoding the heavy-chain of HoAKs-1 antibody including these 57 nucleotides and the predicted amino acid sequence are shown in SEQ ID NO: 118 and SEQ ID NO: 119, respectively. On the other hand, because these 57 nucleotides also contain the sequence encoding the constant region, the nucleotide sequence of the gene encoding the heavy chain of the HoAKs-1 antibody including only variable region (24 nucleotides) and the predicted amino acid sequence are shown in SEQ ID NO: 114 and SEQ ID NO: 115, respectively.

The amplification of a gene encoding the κ-chain of the HoAKs-1 antibody was carried out by PCR using a 5′-side primer of PCR primer VK4 (SEQ ID NO: 27) corresponding to the N-terminal amino acid sequence conserved in the frame 1 of variable region of the κ chain of human antibodies, and a 3′-side primer of PCR primer GKFOR (SEQ ID NO: 109) corresponding to the C-terminal amino acid sequence of constant region of κ chain of human antibodies. The resulting PCR product was inserted into a plasmid in the same way as described above to determine the nucleotide sequence. As a result, a sequence composed of 99 nucleotides (SEQ ID NO: 112) which follows the 3′-side of the above-described nucleotide sequence of variable region of the κ chain (SEQ ID NO: 83) was determined. This nucleotide sequence was predicted to encode 33 amino acids (SEQ ID NO: 113). The nucleotide sequence of the gene encoding the κ-chain of 1-HoAKs-1 antibody including these 99 nucleotides and the predicted amino acid sequence are shown in SEQ ID NO: 120 and SEQ ID NO: 121, respectively. On the other hand, because these 99 nucleotides also contain the sequence encoding the constant region, the nucleotide sequence of the gene encoding the κ chain of HoAKs-1 antibody including only variable region (24 nucleotides and the predicted amino acid sequence are shown in SEQ ID NO: 116 and SEQ ID NO: 117, respectively.

A boundary between the hypervariable region (CDR) and the framework was determined with reference to the literature of Kabat et. al. (Sequences of Proteins of Immunological Interest, fifth edition, National Institutes of Health, Bethesda, Md., 1991). As a result, the CDRs of the heavy chain were determined to be HCDR1 (nucleotide sequence: SEQ ID NO: 85, amino acid sequence: SEQ ID NO: 86), HCDR2 (nucleotide sequence: SEQ ID NO: 87, amino acid sequence: SEQ ID NO: 88), and HCDR3 (nucleotide sequence: SEQ ID NO: 89, amino acid sequence: SEQ ID NO: 90). The CDRs of the light chain were determined to be LCDR1 (nucleotide sequence: SEQ ID NO: 91, amino acid sequence: SEQ ID NO: 92), LCDR2 (nucleotide sequence: SEQ ID NO: 93, amino acid sequence: SEQ ID NO: 94), and LCDR3 (nucleotide sequence: SEQ ID NO: 95, amino acid sequence: SEQ ID NO: 96).

(8) Duration of Morphological Changes

The pancreatic cancer cell line PANC-1 in which morphological changes had been observed by the addition of the HoAKs-1 antibody was used to study the duration of its morphological changes. The pancreatic cancer cell line PANC-1 was cultured for 5 days at 37° C. under 5% CO₂ in the presence of approximately 100 μg/ml of the HoAKs-1 antibody, and then, culture medium was replaced with culture medium free from the HoAKs-1 antibody and cultured for additional 7 days. The microscopic images of the morphology of the cells on 3rd, 6th and 7th days post-removal of the HoAKs-1 antibody are shown in FIG. 6. Morphological changes of the PANC-1 cell caused by the HoAKs-1 antibody were continuously observed for a long term even after the removal of the antibody.

(9) Binding of HoAKs-1 Antibody to Surfaces of Living Cancer Cells

The pancreatic cancer cell line PANC-1, the human lung cancer cell line HLC-1 and the human vascular endothelial cells HUVECs were seeded on a 96-well plate (3603, available from Corning Inc.) and cultured at 37° C. under 5% CO₂ for 1 day. The plate was then added with a solution containing 50 μg/ml of the biotinylated HoAKs-1 antibody described in Example (3)-2 and 0.05% sodium azide, and allowed to react at room temperature for 60 minutes. After the removal of the antibody solution, a solution containing 20 nM of Qdot™565 streptavidin-label (available from Quantm Dot Corporation) and 0.05% sodium azide was added and incubated at room temperature for 30 minutes. After removal of the solution, PBS containing 0.05% sodium azide was added and cells were observed with a confocal fluorescence microscope (CSU10, available from Yokogawa Electric Corporation). The binding of the HoAKs-1 antibody to the surface of each living cell is shown in FIG. 7. The HoAKs-1 antibody exhibited binding to the surfaces of the living cells of the PANC-1 and the HLC-1 (FIGS. 7-A and 7-C), but no binding to the HUVEC cells (FIG. 7-E). The human IgM antibody used as a control exhibited no binding to all of the cells (FIGS. 7-B, 7-D, and 7-F).

(10) Preparation of a Mouse Monoclonal Antibody Against Approximately 55 kDa Protein Derived from Pancreatic Cancer Cell Line PANC-1

(10)-1: Immunization of Mouse and Cell Fusion

The proteins in the insoluble fraction after solubilization with the RIPA buffer were prepared from the homogenate of the PANC-1 cell in the same way as in Example (6)-1. Approximately 180 μg of the proteins were subjected to electrophoresis on 10% acrylamide gel. After electrophoresis, the gel was stained with Coomassie Brilliant Blue and the band corresponding to an approximately 55 kDa protein to which the HoAKs-1 antibody reacted was excised.

The excised gel was fractured and mixed with 0.2 ml of Freund's complete adjuvant (DIFCO LABORATORIES). The mixture was injected intraperitoneally into a mouse (Balb/cA Jcl, 6-week old, female, CLEA JAPAN) to carry out primary immunization. After additional two weeks, the same kind of gel was mixed with incomplete adjuvant and the preparation as prepared as described above was used to immunize the mouse again. After 4 days, the spleen was extracted from the same mouse. Lymphocytes were prepared (2.4×10⁸ cells) and used to fuse to mouse myeloma cells P3U1s according to a standard method (Experimental Manual for Monoclonal Antibody, published by Kodansha Scientific). The fused cells were suspended in the culture medium D (eRDF+50 μg/ml gentamicin+10% FCS) supplemented with usual concentrations of HAT. The suspension was dispensed on a 96-well plate and cultured at 37° C. in a CO₂ incubator. After approximately 2 weeks from cell fusion, the appearance of hybridomas was detected. Using the culture supernatant, reactivity to the approximately 55 kDa protein was detected by Western blotting and thereby a hybridoma of interest was selected.

(10)-2: Detection of Reactivity to Approximately 55 kDa Protein

Approximately 4 mg of the proteins in the insoluble fraction after solubilization of the homogenate of the PANC-1 cell with the RIPA buffer was used for electrophoresis on 10% acrylamide gel. The proteins were transferred from the gel to a PVDF membrane and the membrane was blocked. The culture supernatant was collected from the well of the 96-well plate as described in Example (10)-1 and used to react with the transferred PVDF membrane at 37° C. for 1 hour. The PVDF membrane was washed with PBS-T. The resulting PVDF membrane was added with a HRP-conjugated goat antibody against a mouse antibody (1,000-fold dilution, CAPPEL) and further reacted at 37° C. for 1 hour. Next, the PVDF membrane was washed with PBS-T and the reactivity of the culture supernatant to the approximately 55 kDa protein was determined using Konica Immunostain HRP-1000 (Konica). Cloning of hybridoma was performed by limiting dilution from the wells in which reactivity was detected, and thereby hybridoma cell lines 2F6-1 and 3F9-1 were established.

(11) Binding of an Anti-55 kDa Mouse Monoclonal Antibody to Surfaces of Living Cancer Cells

(11)-1: Purification and Labeling of the Anti-55 kDa Mouse Monoclonal Antibody

The hybridoma cell lines 2F6-1 and 3F9-1 established in Example (10)-2 were cultured. The culture supernatant of each of the hybridoma cell lines was collected and loaded onto the PROSEP-A to purify the antibody. Each monoclonal antibody was found to be IgM by SDS-PAGE analysis. After each of the purified antibodies was biotinylated using a biotinylation reagent according to the manufacturer's instructions, the labeled antibody was separated from free biotin by a gel filtration method.

(11)-2: Binding of the Antibody to Surface of Living Cancer Cells

The pancreatic cancer cell line PANC-1, the lung cancer cell line HLC-1, and the vascular endothelial cells HUVECs were seeded on a 96-well plate (3603, Corning) and cultured at 37° C. under 5% CO₂ for 1 day in the same way as in Example (9). The plate was then added with a solution containing 50 μg/ml of the biotinylated anti-55 kDa mouse monoclonal antibody described in Example (11)−1 and 0.05% sodium azide, and allowed to react at room temperature for 60 minutes. After the removal of the antibody solution, a solution containing 20 nM of Qdot™565 streptavidin-labeled (Quantm Dot Corporation) and 0.05% sodium azide was added and reacted at room temperature for 30 minutes. After removal of the solution, PBS containing 0.05% sodium azide was added and cells were observed with a confocal fluorescence microscope (CSU10, Yokogawa Electric Corporation). The binding of the anti-55 kDa mouse monoclonal antibody to the surface of each living cell is shown in FIG. 8. The antibody derived from 2F6-1 and 3F9-1 exhibited binding to the surfaces of the living cells of the PANC-1 and the HLC-1 like HoAKs-1 antibody described in Example (9) (FIGS. 8-A, 8-B, 8-D, and 8-E), but exhibited no binding to the HUVECs cells (FIGS. 8-G and 8-H).

(12) Reactivity of Anti-Vimentin Antibody and Anti-Desmin Antibody to Approximately 55 kDa Protein Evaluated by Western Blotting

The proteins in the insoluble fraction after solubilization of the homogenate of the PANC-1 cells with the RIPA buffer was loaded onto the lanes of 10% acrylamide gel at approximately 10 μg/lane for electrophoresis. The proteins were transferred from the gel to a PVDF membrane and the membrane was blocked. An anti-vimentin mouse monoclonal antibody (sc-6260, Santa Cruz Biotechnology) or an anti-desmin goat antibody (sc-7559,Santa Cruz Biotechnology) was reacted with the PVDF membrane at 37° C. for 1 hour. The PVDF membrane was then washed with PBS-T and added with a HRP-conjugated goat antibody against a mouse antibody (1,000-fold dilution, CAPPEL) or HRP-conjugated mouse antibody against a goat antibody (1,000-fold dilution), and further reacted at 37° C. for 1 hour. Next, the PVDF membrane was washed with PBS-T and substances that reacted to the antibodies were detected using Western blotting luminol reagent. Although the anti-vimentin antibody exhibited reactivity to the approximately 55 kDa protein, the anti-desmin antibody exhibited no reactivity.

Those results have demonstrated that the approximately 55 kDa protein derived from the PANC-1 that was recognized by the HoAKs-1 antibody is determined to be vimentin and that there exists an antibody having binding ability to the surface of the living cancer cells among the antibodies having reactivity to the protein.

(13) Preparation of γ-HoA. (Recombinant HoAKs-1 Antibody)

(13-1) Preparation of cDNA and Cloning of a DNA Fragment Encoding a Variable Region of HoAKs-1

The preparation of cDNA from the total RNA (described in Example (7)) and the PCR reaction were carried out using Perkin Elmer Gene Amp PCR System 2400 and ThermoScript™ RT-PCR Systems plus platinum Tag DNA polymerase High Fidelity (Invitrogen) according to the manufacturer's instructions. Random hexamers supplied in the kit were used as primers for preparing the cDNA of the heavy chain. P1 (SEQ ID NO: 122) was used as a primer for preparing the cDNA of the κ chain.

For amplification of the variable regions of the heavy chain and the κ chain, primers having a restriction enzyme site for insertion into an expression plasmid were used. For amplification of the variable region of the heavy chain, primer P2 (SEQ ID NO: 123) containing a HindIII site and a signal sequence at the 5′ terminus and primer P3 (SEQ ID NO: 124) containing a NheI site at the 3′ side were used. For amplification of the variable region of the κ chain, primer P4 (SEQ ID NO: 125) containing a HindIII site and a signal sequence at the 5′ side and primer P5 (SEQ ID NO: 126) containing a BsiWI site at the 3′ side were used.

The DNA fragment of the variable region of each of the amplified heavy and κ chains was purified using QIAquick™ PCR Purification Kit (QIAGEN). Next, for insertion into the expression vector, the DNA fragments were digested with restriction enzymes. The fragment of the heavy chain was digested with HindIII and NheI at 37° C. for 2 hours. The DNA fragment of the κ chain was initially digested with BsiWI at 37° C. for 2 hours and then purified with the QIAquick™ PCR Purification Kit (QIAGEN), followed by subsequent digestion with HindIII at 37° C. for 2 hours. The digested DNA fragments were subjected to 1.5% agarose electrophoresis to purify a DNA fragment of interest using a QIAquick™ Gel Extraction Kit (QIAGEN).

(13-2) Digestion of Expression Plasmid and Preparation of Plasmid Fragment

For expressing the human IgG1-type recombinant antibody of the HoAKs-1, pEX-G1-WLpHy containing the sequence of the constant region of the heavy chain was used as a plasmid for expressing the heavy chain, and pKS-κ′-Hind-5 containing the sequence of the constant region of the κ chain was used as a plasmid for expressing the κ chain. The pEX-G1-WLpHy was digested with HindIII and SpeI at 37° C. for 2 hours. The pKS-κ′-Hind-5 was digested with Asp718 at 37° C. for 2 hours and then purified with a QIAquick™ PCR Purification Kit (QIAGEN), followed by subsequent digestion with HindIII at 37° C. for 2 hours. The digested fragments were subjected to 0.8% agarose electrophoresis to purify a fragment of interest using QIAquick™ Gel Extraction Kit (QIAGEN).

(13-3) Insertion of HoAKs-1 Variable Region into the Expression Plasmid

The DNA fragment containing heavy chain of the variable region of the HoAKs-1 obtained by the above-described method was inserted into the digested expression plasmid pEX-G1-WLpHy using Ligation Kit Ver. 2.1 (TAKARA BIO INC.) according to the manufacturer's instructions, and the obtained plasmid was used to transfonn E. coli DH5α-T1 (Invitrogen) according to the manufacturer's instructions. The appeared colonies were picked up and the plasmid was purified using QIAprep™ Spin Miniprep Kit (QIAGEN). The plasmid containing the nucleotide sequence of the heavy chain was digested with NdeI at 37° C. for 1 hour and subjected to 1.5% agarose electrophoresis, and thereby a desired plasmid pEX-HoAKs-H was obtained. For the obtained plasmid, the nucleotide sequence was analyzed using P6 primer (SEQ ID NO: 127) at the 5′ side and P7 primer (SEQ ID NO: 128) at the 3′ side. The nucleotide sequence of the structural gene of the heavy-chain of the HoAKs-1 recombinant antibody is shown in SEQ ID NO: 129.

On the other hand, the DNA fragment containing the variable region of the κ chain of the HoAKs-1 was inserted into the digested expression plasmid pKS-κ′-Hind-5 using Ligation Kit Ver. 2.1 (TAKARA BIO INC.) according to the manufacturer's instructions, and the obtained plasmid was used to transform E. coli DH5α-T1 (Invitrogen). The appeared colonies were picked up and the plasmid was purified using QIAprep™ Spin Miniprep Kit (QIAGEN). The plasmid containing the nucleotide sequence of the κ chain was digested with BsiWI at 37° C. for 1 hour and subjected to 1.5% agarose electrophoresis, and thereby a desired plasmid pKS-HoAKs-K was obtained. For the obtained plasmid, the nucleotide sequence was confirmed using primer P6 at the 5′ side and primer P1 at the 3′ side. The nucleotide sequence of the structural gene of the κ-chain of the HoAKs-1 recombinant antibody is shown in SEQ ID NO: 131.

(13-3) Insertion of a Gene Encoding Heavy Chain of HoAKs-1 into a Plasmid Containing HoAKs-1 κ Chain

For ligating the heavy chain and κ chain of HoAKs-1 on one plasmid, the plasmids obtained above were digested with restriction enzymes. The pEX-HoAKs-H was digested with NheI at 37° C. for 2 hours and the pKS-HoAKs-K was digested with NheI and SpeI at 37° C. for 2 hours. The resulting fragments were purified using QIAquick™ PCR Purification Kit (QIAGEN). The fragments were ligated with each other using Ligation Kit Ver. 2.1 (TAKARA BIO INC.) according to the manufacturer's instructions, and the obtained plasmid was used to transform E. coli DH5α-T1 (Invitrogen). The appeared colonies were picked up and the plasmid was purified using QIAprep™ Spin Miniprep Kit (QIAGEN). The resulting plasmid was digested with NheI at 37° C. for 30 minutes and subjected to 0.8% agarose electrophoresis, and thereby a desired plasmid pEX-HoAKs-HK was obtained.

(13-4) Construction of γ-HoA.-Expressing Plasmid

The pEX-HoAKs-HK obtained above was ligated with a plasmid pSV2dhfr″ containing a dhfr gene to construct a plasmid for expressing γ-HoA. The pEX-HoAKs-HK was first digested with BamHI and NheI at 37° C. for 2 hours and then subjected to 0.8% agarose electrophoresis, followed by purification of a DNA fragment of interest using QIAquick™ Gel Extraction Kit (QIAGEN). The pSV2dhfr″ was digested with BamHI and NheI at 37° C. for 2 hours and then treated at 65° C. for 15 minutes by the addition of Alkaline Phosphatase (TAKARA BIO INC.), followed by purification using QIAquick™ PCR Purification Kit (QIAGEN). Thereafter, the resulting mixture was subjected to 0.8% agarose electrophoresis, and a DNA fragment of interest was purified using QIAquick™ Gel Extraction Kit (QIAGEN).

The fragments were ligated with each other using Ligation Kit Ver. 2.1 (TAKARA BIO INC.) according to the manufacturer's instructions, and the obtained plasmid was used to transform E. coli DH5α-T1 (Invitrogen). The appeared colonies were picked up and the plasmid was purified using QIAprep™ Spin Miniprep Kit (QIAGEN). The resulting plasmid was digested with NdeI at 37° C. for 1 hour and subjected to 1.5% agarose electrophoresis, and thereby a desired plasmid pEX-HoAKs-HK/pSV2dhfr″ for expression of recombinant antibody was obtained.

(13-5) Preparation of γ-HoA.-Producing Cells

CHO (DG325) cell lines culturable in a serum-free medium were used as cell lines for producing γ-HoA. The CHOs (DG325) were diluted in CHO-S-SFMII (GIBCO) at 1×10⁶ cells/ml. Thereafter, 2 μg of pEX-HoAKs-HK/pSV2dhft″ DNA and 6 μL of FuGENE™ 6 transfection reagent (Roche) were mixed to transfect the CHOs (DG325) according to the manufacturer's instructions. At 5 hours after transfection, EX-CELL325-PF (Nichirei) was added. After two-day culture, 400 μg/ml of G418 Sulfate (Promega) and 0, 25, or 50 nM of methotrexate (Sigma) were added to the medium for selection and culture was further conducted, and thereby γ-HoA.-producing cells were obtained.

(13-6) Measurement of Production Amount of Antibody Using ELISA Assay

The amount of γ-HoA. produced by the cells was measured by sandwich ELISA assay. At first, a rabbit anti-human immunoglobulin antibody (CAPPEL) was diluted to 50 μg/ml with the solution 1 (PBS) and added to a 96-well flexible plate (FALCON) at 50 μL/well to treat at 37° C. for 2 hours. The solution in the wells was then discarded and the solution 2 (0.1% Gelatin/PBS/0.05% Tween 20) was added to the wells at 200 μL/well to react at 4° C. for 16 or more hours. The solution in each of the wells was then discarded and the plate was added with 50 μL/well of the culture supernatant diluted with the solution 2 to incubate at 4° C. for 16 or more hours. After reaction, the solution in each of the wells was discarded. After washed five times with a solution 3 (PBS/0.05% Tween 20), the plate was added with 50 μL/well of a HRP-labeled rabbit anti-human immunoglobulin antibody (CAPPEL) which had been diluted 1,000-fold with the solution 2, and reacted at 37° C. for 1 hour. The solution in each of the wells was discarded. After washing five times with PBS/0.05% Tween 20, the plate was added with 50 μL/well of substrate solution (light-shaded and adjusted before use) in which an o-phenylenediamine tablet (Wako Pure Chemical Industries) had been dissolved in 50 mM citrate buffer (pH 5.0) and supplemented with hydrogen peroxide solution. After the plate was reacted at room temperature for about 3 minutes for color development, 1 N H₂SO₄ was added at 50 μL/well to terminate the reaction. Absorbance A1 at L1=495 nm and absorbance A2 at L2=650 nm were measured with a multi-plate reader SPECTRA MAX250 (Molecular Devices), and the value of “A1-A2” was calculated. Human IgG1κ (CAPPEL) was diluted and used as a standard solution. A calibration curve was made to calculate the amount of the antibodies in the culture supernatant. From the calculated result, a cell having the largest amount of the antibody production was selected and used for producing γ-HoA.

(13-7) Purification of γ-HoA.

The γ-HoA.-producing cell line obtained above was cultured in EX-CELL325-PF (Nichirei) supplemented with G418 Sulfate (Promega) and methotrexate (Sigma) to obtain a culture medium containing γ-HoA. Next, the culture medium was loaded onto the PROSEP-A for adsorbing the γ-HoA. on it. The adsorbedy-HoA. was then eluted and thereby the γ-HoA. was purified. It was confirmed that the γ-HoA. was a pure IgG by SDS-PAGE (not shown).

(14) Detection of Reactivity of γ-HoA. to Approximately 55 kDa Protein Derived from Pancreatic Cancer Cell Line PANC-1

Each 10 μg of the proteins in the insoluble fraction after solubilization of the homogenate of the PANC-1 cell with the RIPA buffer was subjected to electrophoresis on 10% acrylamide gel. The protein was transferred from the gel to a PVDF membrane and the membrane was blocked. The transferred PVDF membrane was reacted with the purified γ-HoA. described in Example (13-7) at 37° C. for 1 hour. The PVDF membrane was washed with PBS-T. The resulting PVDF membrane was added with an HRP-conjugated goat antibody against a human antibody (1,000-fold dilution, CAPPEL) and further reacted at 37° C. for 1 hour. Next, the PVDF membrane was washed with PBS-T. The reactivity of the γ-HoA. to the approximately 55 kDa protein was detected by using Western blotting luminol reagent (Santa Cruz Biotechnology), which revealed that the γ-HoA. had reactivity to the approximately 55 kDa protein like the HoAKs-1 antibody.

(15) Binding of γ-HoA. to Surfaces of Living Cancer Cells

The pancreatic cancer cell line PANC-1, the lung cancer cell line HLC-1 and the vascular endothelial cells HUVECs were seeded on a 96-well plate (3603, Corning) and cultured at 37° C. under 5% CO₂ for 1 day. The plate was then added with a solution containing the purified γ-HoA. described in Example (13)-7 and 0.05% sodium azide, and reacted at room temperature for 60 minutes. After the removal of the γ-HoA. solution, the plate was added with a solution containing FITC-conjugated goat antibody against a human antibody diluted 20-fold (CAPPEL) and 0.05% sodium azide and reacted at room temperature for 30 minutes. After removal of the solution, PBS containing 0.05% sodium azide was added and cells were observed with a confocal fluorescence microscope (CSU10, Yokogawa Electric Corporation). The binding of the antibody to the surface of each living cell is shown in FIG. 9. The γ-HoA. exhibited binding to the surfaces of the living cells of the PANC-1 and the HLC-1 (FIGS. 9-A and 9-C), but no binding to the HUVEC cells (FIG. 9-E), like the HoAKs-1 antibody described in Example (9).

INDUSTRIAL APPLICABILITY

By using a monoclonal antibody obtained in the present invention, an anti-cancer drug that selectively attacks cancer tissues, particularly non-small cell lung cancer, pancreatic cancer or gastric cancer can be provided. Moreover, when the human monoclonal antibody of the present invention is used, an anti-cancer drug capable of continuous administration with reduced side effects can be provided. 

1. An isolated monoclonal antibody which specifically binds human vimentin and which has a heavy chain and a light chain, wherein the variable region of the heavy chain of said the monoclonal antibody comprises the amino acid sequences of SEQ ID NOS: 86, 88 and 90, and wherein the variable region of the light chain of the monoclonal antibody comprises the amino acid sequences of SEQ ID NOS: 92, 94 and
 96. 2. The monoclonal antibody according to claim 1, wherein the variable region of the heavy chain comprises the amino acid sequence of SEQ ID NO:
 82. 3. The monoclonal antibody according to claim 1, wherein the variable region of the heavy chain comprises the amino acid sequence of SEQ ID NO:
 115. 4. The monoclonal antibody according to claim 1, wherein the variable region of the light chain comprises the amino acid sequence of SEQ ID NO:
 84. 5. The monoclonal antibody according to claim 1, wherein the variable region of the light chain comprises the amino acid sequence of SEQ ID NO:
 117. 6. The monoclonal antibody according to claim 1, wherein the variable region of the heavy chain contains the amino acid sequence of SEQ ID NO: 82, and the variable region of the light chain comprises the amino acid sequence of SEQ ID NO:
 84. 7. The monoclonal antibody according to claim 1, wherein the variable region of the heavy chain comprises the amino acid sequence of SEQ ID NO: 115, and the variable region of the light chain comprises an the amino acid sequence of SEQ ID NO:
 117. 8. The monoclonal antibody according to claim 1, wherein said monoclonal antibody is a human antibody.
 9. An isolated DNA which encodes the monoclonal antibody according to claim
 1. 10. The DNA according to claim 9, wherein the variable region of the heavy chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NOS: 85, 87 and 89, and a region that encodes the variable region of the light chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NOS: 91, 93 and
 95. 11. The DNA according to claim 9, wherein the variable region of the heavy chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NO: 81, and the variable region of the light chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NO:
 83. 12. The DNA according to claim 9, wherein the variable region of the heavy chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NO: 114, and the variable region of the light chain of the monoclonal antibody is encoded by a nucleotide sequence comprising SEQ ID NO:
 116. 13. An isolated recombinant vector comprising the DNA according to claim
 9. 14. An isolated transformant, comprising the recombinant vector according to claim
 13. 15. A pharmaceutical composition, comprising the monoclonal antibody according to claim
 1. 16. A diagnostic reagent, which comprises the monoclonal antibody according to claim
 1. 